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Comment by JKCalhoun | Hacker News Reader

This is HN, I can be cynical, right? Allow me to air one of my pet peeves: articles that make the threat of an asteroid collision with Earth something we should be afraid of. (Oh, and films of course.)

I never understood why anyone should give it any more than even a passing thought. As a layman my understanding is that the last great extinction event from an asteroid was like (Wikipedia tells me) 66 million years ago.

With that frequency/odds my fears seem much better afforded toward the dangers of climate change or any number of other issues that likely will have repercussions in my or my grandchildren's lifetimes.

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In between the extinction-level asteroids and the mostly harmless ones is a medium-size class of asteroids about the size of a football pitch. Those are the scary ones. They are small enough to be hard to spot, and there are enough of them that one of them hits earth every 10,000 years or so. They have not been a big deal in the past. They don't cause mass extinctions, but they are more than big enough to bring about the end of civilization. If one of them hits an ocean (which is the most likely scenario) it will cause global tsunamis that will make the Fukushima event look like a small ripple. We're talking waves many hundreds of meters high. Not a single coastal city bordering the ocean where the asteroid hits would survive.

This is an excellent way to do what-if scenarios https://neal.fun/asteroid-launcher/

Meh, I dropped one like GP mentioned in the north atlantic and other than mentioning the size of the Tsunami, all of the other factors assumed it was dropped within miles of land.

We don't know when the next big one is coming, because we don't have perfect knowledge of all objects in (or travelling through) our solar system.

On the scale of things to be concerned about, I'd agree that Climate Change is definitely something that we should be proportionally spending more resource on.

We have the capability of solving multiple problems at once, though - it's not an all-or-nothing thing. So I think running observation/detection systems is worth it, even with the occasional news release about significant close-approaches.

> We have the capability of solving multiple problems at once, though - it's not an all-or-nothing thing. So I think running observation/detection systems is worth it, even with the occasional news release about significant close-approaches.

Well said, I agree. This applies to a lot of things that people often ask, “but shouldn’t we focus on X instead?” about.

We have both the people and the resources to do multiple things at once, and we should, if only because it doesn’t help anybody to tell people who’ve spent a large chunk of their lives working on asteroid defense, rockets, crewed spaceflight, etc that their job is gone and they have to start over from scratch and work on X instead.

The great extinction events are just icing on the cake. We get hit by rocks quite often, one of the most recent notable ones being the one that caused the Burckle Crater in the Indian ocean. The crater is 29km in diameter and the impact happened roughly 5000 years ago. The ocean impact would have created a mega-tsunami that devastated the coastlines of Australia, India, Africa, and South Asia. God knows what the fallout from it would have looked like but it would have vaporized a lot of water and also flung masses of ejecta into the atmosphere. Land impacts can be a lot worse since the damage isn't just limited to the impact site, that ejecta again creates a large radius of splash damage. Then there are the fires, the smoke, a nice dusting of radioactive material, and don't forget the shockwave and overpressure.

We've been lucky so far but you'd have to be a fool to rely on luck forever.

> This is HN, I can be cynical, right?

Your comment isn't cynical, it is more akin to a lucid perspective of a set of threats.

The economy and threats to democratic process are more worrisome -- and yet at the same time, much more within our capability to fix than an asteroid strike.

For a lucid fictional presentation of an asteroid strike, I recommend "Lucifer's Hammer" by Niven and Pournelle.^1

[1] https://en.wikipedia.org/wiki/Lucifer%27s_Hammer

Yeah super volcanos and solar flares on the other hand... <I don't know how likely those are either, but they seem superscary isn't yellowstone overdue?>

For what it's worth, Yellowstone's upper lava chamber is 5% molten and the lower magma chamber is about 2% molten. To get eruptions that percentage has to be much higher as it is in the Hawaiian volcanoes. Scientists have differing opinions on how many years it will take to reach that level but all of their numbers are well over 10k years. I had to look into this prior to moving near it.

Still, I fear for my offspring... a man has no path to immortality, save for his precious seed from his loins, and women their ovaries.

What if an asteroid hits it?

Good timing on the question. We are about to pass through a chunkier part of the Taurid asteroid belt. If the rock is big enough to turn everything molten then I suppose it might be time to hitch a ride in a nuclear submarine.

Yes, a super massive strike is likely very rare and does not happen very often. But smaller asteroids hit the planet more frequently (relatively speaking), yet would still cause a huge catastrophe. It wouldn't cause a mass extinction, but it would still... suck.

The fact that it happened so long ago makes it more likely to happen sooner. Also, my understanding is that we don't really have a good grasp of what's out there outside of of the immediate vicinity of Earth. There are millions and millions of them hurling through our system. A planet-killer can show up on our radar any day.

Wait, isn't that the Gambler's Fallacy?

Gamblers fallacy is about independent probably - there are cyclical natural catastrophes.

> there are cyclical natural catastrophes

That sounds very made up.

I don’t really follow astrophysics, but there were hypotheses that the motion of the solar system through the galactic plane, which has a periodicity, would induce impact events. A cursory search suggests that recent analyses of crater data may not support those hypotheses. Here’s a link to a 2011 paper suggesting as much.

So the notion was certainly a reasonable one even if not ultimately true.

https://academic.oup.com/mnras/article/416/2/1163/1058876

It's way beyond a three body problem though, so it's chaotic even if it's recurrent... even trying to retrodict precise correlations in celestial events 10k years ago is difficult, doing this would be way harder. The only thing I can think of on that scale that's somewhat predictable within meaningful margins is Milankovich cycles. Cool paper though. Thanks for sharing.

(And to note: I can't edit my reply now but I read 'there' as 'these'. Obviously there are other (somewhat) cyclic natural catastrophes especially on shorter timescales.)

Sounds a little like Nemesis [1].

The Wikipedia article mentions 26 million year intervals. So we're probably good for another 10 million?

[1] https://en.wikipedia.org/wiki/Nemesis_(hypothetical_star)

The nature of orbits makes the "cyclical" aspect seem reasonable to me. Especially in light of how many objects there are that have extremely elliptical orbits which dip into the inner solar system and out to the Kuiper belt. Or, objects that end up in a resonance that seems stable enough but are modeled to eventually be perturbed into a new orbit.

Well, we know for a fact that every once in a while, we get hit by an asteroid (which is exactly what this is about). I'd call that cyclical and not made up.

Everyone once in a while the roulette ball lands on green and I get a big payout. That's not a cyclical event.

Only because you don't have the money or time to keep playing. But continue playing for 1 million years, and the black and red will hit a similar number of times and the green a proportionally lower number of times.

Hurricanes are cyclical. It’s not made up. I’m sure there’s a season for tornadoes and blizzards as well.

We have a good idea of how many planet-killer asteroids are out there and that we have detected 90% of them. And 100% of the extinction-level asteroids. Planet-killer asteroids are large, kilometers in diameter, and visible. This asteroid is 10m in diameter, way harder to detect which is why didn't detect it until last minute.

The current goal of NASA asteroid detection is 90% of 150m asteroids which can cause regional disaster.

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